1. Field of the Invention
The present invention relates to an information recording disc for recording control information in a burst cutting area (BCA), an information reproducing drive for reproducing information by using an information recording disc for recording information signals including program data, audio information and video information and an information reproducing system including the information reproducing drive.
2. Description of the Prior Art
Conventionally, a floppy disk, a hard disk, a compact disc read-only memory (CD-ROM), etc. are known as information storage media for storing program data, audio information and video information. Especially, since the CD-ROM is a portable medium having a storage capacity exceeding 600 MB and can be manufactured at low cost, the CD-ROMs have come into wide use for distributing various software.
On the other hand, thanks to recent remarkable improvements of performance of personal computers, it has become possible to handle audio and video (AV) data on the personal computers. For example, applications in which digital moving picture data files employing a video compression method called “Moving Picture Experts Group 1” (MPEG1) are recorded in the CD-ROM or the like and are distributed are on the increase. However, the MPEG1 has high compression ratio but suffers from extraordinary deterioration of video. Therefore, these applications are unsuitable for a case requiring high-quality video such as movies.
Thus, an advanced video compression method called “Moving Picture Experts Group 2” (MPEG2) and an optical disc having a capacity as large as 5 GB, i.e., a digital versatile disc (DVD) have been developed in recent years. By combining these two technologies, the DVD is capable of recording high-quality digital AV data for not less than two hours and therefore, is fully expected to serve as a next-generation AV data storage medium. Systems for reproducing the DVD are roughly classified into two groups. One of the systems belongs to a field of consumer electronics and is called a DVD player in which a functional block for reproducing compressed AV data from the DVD and a functional block for expanding the compressed AV data are integrated. The other system belongs to a field of computers and is a computer system which includes a DVD drive and an AV decoding card. The DVD drive has a function of reproducing compressed AV data and control data of contents from the DVD, while the AV decoding card has a function of expanding the compressed AV data. These two devices are independent of each other and are installed into a computer. For example, the DVD drive is provided in an expansion bay of the computer, while the AV decoding card is inserted into an expansion slot of the computer. Through control of the computer, the compressed AV data reproduced by the DVD drive is expanded by the AV decoding card on the basis of the control data reproduced by the DVD drive such that AV data is reproduced. A computer system in which a video CD player, a CD-ROM drive and a MEPEG1 decoder board are incorporated is similar to this configuration.
However, since the system in the field of consumer electronics and the system in the field of computers can reproduce the same medium, i.e., the DVD, it is, in fact, difficult to copyright protect, etc. International Publication No. WO97/14147 discloses a technique for copyright protecting and a technique for classifying apparatuses according to applications or regions. In this prior art document, by using an information recording medium in which scrambled (or enciphered) data and key information for descrambling are recorded, descrambling circuits are provided in information reproducing apparatuses and mutual authentication for safely exchanging the key information among the information reproducing apparatuses is performed, whereby an aim of copyright protecting is achieved. Meanwhile, descrambling varying according to applications or regions is performed and the information reproducing apparatuses are classified according to kinds of the descrambling circuits of the information reproducing apparatuses into ones in which descrambling is possible and the remainder in which descrambling is not possible.
By classifying the information reproducing apparatuses according to regions, ethical problems can be solved. Ethical ideas depend on climates, customs and religions of countries and therefore, vary according to countries. Hence, such a case may happen that contents which offer no ethical problem in one country pose an ethical problem in another country. In such a case, it is necessary to adopt a measure for preventing reproduction of the ethically undesirable contents in the latter country.
Hereinafter, a conventional method of classifying information reproducing apparatuses according to regions is described. FIGS. 6 and 7A to 7D show the data structure of a known AV data recording disc 400. In FIGS. 6 and 7A to 7D, the known AV data recording disc 400 is sectioned into information recording units called “sectors” and is divided into a lead-in area 402 for recording control information referred to by the information reproducing apparatuses, a lead-out area 403 and a data recording area 401 for mainly recording user data. Each sector includes a sector header area in which a data identifier (ID) for identifying the sector, etc. are recorded and a user data area in which control information, user data, etc. are recorded. FIG. 6 shows the known AV data recording disc 400, while FIGS. 7A to 7D show the lead-in area 402 of the known AV data recording disc 400. Namely, FIG. 7A shows the lead-in area 402 of the known AV data recording disc 400 of FIG. 6, FIG. 7B shows a control data area of the lead-in area 402 of FIG. 7A, FIG. 7C shows physical format information in the control data area of FIG. 7B and FIG. 7D shows disc region information 405 in the physical format information of FIG. 7C.
This known AV data recording disc 400 is characterized in that a sector storing the disc region information 405 exists in a sector header area of the lead-in area 402. The lead-in area 402 is constituted by blank areas in which “00h” (h=hexadecimal number) is recorded, a reference signal area in which a reference signal for reproduction is recorded and the control data area in which the control information referred to by the information reproducing apparatuses is recorded. In the control data area of FIG. 7B, identical information is recorded in 192 control data blocks each constituted by 16 sectors. The physical format information is recorded in the first sector of the control data block. In a user data area of the physical format information, physical information such as disc type information indicative of a read-only disc or a rewritable disc and disc size information indicative of a size of 120 mm or 80 mm of the disc is recorded.
On the other hand, in the sector header area of the physical format information, the disc region information 405 is recorded together with the data ID and ID error detection (IED) acting as a code for detecting error in the sector header area. The disc region information 405 is constituted by region n flags (n=integer from 0 to 7) which indicate whether or not reproduction in each of eight divided regions is permitted. When a flag corresponding to a region in which the information reproducing apparatus is installed is set to “1”, it means that reproduction in the region is permitted. In order to perform such reproduction control, the information reproducing apparatus should possess information corresponding to the region for its installation and have a function of stopping reproduction in case this information is not coincident with the disc region information 405.
Meanwhile, peripheral devices in the computer market are common throughout the world and are contrary to DVD players, etc. in the consumer electronics market, for which distribution channels are built up in respective regions due to different power source voltages among the regions or different standards for video signals such as “National Television System Committee” (NTSC) and “Phase Alternation by Line” (PAL). Thus, in cost and distribution, apparatuses whose specifications vary according to regions are disadvantageous for users. On the other hand, if regional information of the apparatuses is rewritable from outside, the regional information can be newly changed to illicit regional information any number of times and thus, reproduction control in each of the regions does not function properly.
Therefore, in the DVD drive acting as a conventional peripheral device for computers, a scheme is introduced in which the regional information of the apparatuses can be updated only a limited number of times. In this scheme, the disc region information 405 of the AV data recording disc 400 inserted by the user is basically regarded as corresponding to a region for installation of the information reproducing apparatus so as to be stored, as a regional code of the information reproducing apparatus, in a nonvolatile memory and the regional code of the information reproducing apparatus can be changed only an initial predetermined number of times.
Hereinafter, a conventional regional information control method is described with reference to FIGS. 8 and 9. FIG. 8 shows a configuration of a conventional information reproducing system 500. The conventional information reproducing system 500 includes a host computer 510 and a disc reproducing drive 520 which are connected to each other by a device interface bus 550. The host computer 510 includes a central processing circuit 511, a main storage 512, a processor bus 513, an external bus 515, an interface control card 516 for performing protocol control with the disc reproducing drive 520, a magnetic disk unit 517 and an AV data decoding card 518 for converting compressed digital AV data into analog AV signals.
Meanwhile, the disc reproducing drive 520 includes an interface control circuit 521 connected to the host computer 510, a data read-out means 523 for reading various information from the AV data recording disc 400, a regional information comparing means 524 for deciding whether or not the disc region information 405 of the AV data recording disc 400 is coincident with installation region information of an installation region information memory 526 of the disc reproducing drive 520, a reproduction control means 522 for effecting changeover between prohibition and permission of delivery of AV data 540 of the AV data recording disc 400 in accordance with the decision of the regional information comparing means 524, an installation region information updating means 527 for updating the installation region information memory 526 and a regional information setting counter 525 only a limited number of times and a control bus 528.
FIG. 9 shows sequence in which the conventional information reproducing system 500 reproduces the AV data 540 recorded in the AV data recording disc 400. In response to a request for data reproduction from a user at step S600, reproduction application software stored in the main storage 512 issues a command of reproduction of the AV data 540 to the disc reproducing drive 520 via the interface control card 516 at step S601. In response to the reproduction command from the interface control circuit 521, the reproduction control means 522 advances to the regional information comparing means 524 a request for comparison and decision of the regional information. In response to this request from the reproduction control means 522, the regional information comparing means 524 issues an instruction of read-out of the disc region information 405 to the data read-out means 523 at step S602. By comparing the read disc region information 405 and the installation region information of the installation region information memory 526 with each other in the regional information comparing means 524, a decision is made at step S603 as to whether or not the disc region information 405 permits reproduction in a region indicated by the installation region information memory 526.
In the case of “YES” at step S603, the reproduction control means 522 issues an instruction of read-out of the AV data 540 to the data read-out means 523 at step S604. Through the reproduction control means 522 and the interface control circuit 521, the AV data 540 is converted into analog AV signals by the AV data decoding card 518 in the host computer 510 so as to be outputted at step S605. On the other hand, in the case of “NO” at step S603, the host computer 510 requests transfer of the disc region information 405. In response to the request for transfer of the disc region 405, the reproduction control means 522 transfers the disc region information 405 from the data read-out means 523 to the host computer 510 at step S607. Then, at step S608, the host computer 510 issues to the disc reproducing drive 520 a request for update of the installation region information so as to make the installation region information of the installation region information memory 526 coincident with the disc region information 405.
In response to the update request from the host computer 510 via the interface control circuit 521, the installation region information updating means 527 decides whether or not count of the regional information setting counter 525 is zero at step S609. In the case of “YES” at step S609, a report of error is issued to the host computer 510 at step S610 by judging that setting has been already performed the permissible limited number of times. In this case, the AV data 540 on the AV data recording disc 400 is not reproduced. On the other hand, in the case of “NO” at step S609, the installation region information updating means 527 updates the installation region information of the installation region information memory 526 to the disc region information 405 at step S611 and count of the regional information setting counter 525 is decremented by 1 at step S612. Subsequently, the program flow returns to step S601. At this time, since the installation region information of the installation region information memory 526 is coincident with the disc region information 405, reproduction of the AV data 540 is performed normally.
However, in the conventional regional information setting method referred to above, in a case a where a virus program which continuously issues a request for change of the installation region information of the installation region information memory 526 from the host computer 510, such a problem may arise that since the installation region information has been updated the limited number of times while being set to the regional information irrelevant to the installation region, it is impossible to change the installation region information of the installation region information memory 526. In such a case, even if the AV data recording disc 400 conforms to the installation region, the user cannot reproduce the AV data recording disc 400.
In order to solve this problem, it is necessary to provide a recovery means which recovers the installation region information from a state where the installation region information cannot be changed while being set to the regional information irrelevant to the installation region and enables new setting of the installation region information. However, if the recovery means is made available for general users, the installation region information can be changed any number of times, so that the original purpose of performing reproduction control in accordance with the installation region cannot be attained.
Consequently, only a limited number of persons such as a manufacturer of the disc reproducing drive or the information reproducing system should be entitled to execute the above mentioned recovery means. Furthermore, instead of a scheme that the recovery means is materialized by only a software program which operates on a host computer and can be copied and distributed easily, it is necessary to adopt a safe scheme including an equipment whose copying is difficult.